The use of a cyclone, or multiple cyclones connected in parallel or series, has long been known to be advantageous in the separation of particulate matter from a fluid stream. Typically, a relatively high speed fluid stream is introduced tangentially to a generally cylindrical or frusto-conical container, wherein the dirty air stream is accelerated around the inner periphery of the container. The centrifugal acceleration caused by the travel of the fluid in a cyclonic stream through the cyclone causes the particulate matter to be disentrained from the fluid flow and, eg., to collect at the bottom of the container. A fluid outlet is provided for the extraction of the fluid from the centre of the top of the cyclone container, as is well known in the art.
A typical flow path in a cyclone separator is as follows. Fluid to be treated is introduced tangentially at a fluid inlet located at the upper end of the cyclone container (if the cyclone container is vertically disposed). The fluid stream rotates around the inner surface of the cyclone container, and spirals generally downwardly around the inner surface. At the bottom end of the cyclone container the fluid stream travels radially inwardly, generally along the bottom of the container and then turns upwardly and proceeds vertically up and out of the cyclone container. The particulate matter separating action of the cyclonic flow occurs substantially around the inner surface. Once the air moves inwardly to the centre of the container, and upwardly there through, there is little or no dirt separation achieved.
Various types of vacuum cleaners are traditionally produced. These include built in vacuum cleaners, canister vacuum cleaners and upright vacuum cleaners. Upright vacuum cleaners have a ground engaging portion (a cleaning head) and an upwardly extending or main body portion. The ground engaging portion typically has wheels for movement of the cleaning head across a floor and a suction inlet for the intake of dirty air into the vacuum cleaner. The upwardly extending portion comprises the filter means for removing dirt which is entrained in the air. The upwardly extending portion generally has a handle for guiding the vacuum cleaner across the floor.
Traditionally in upright vacuum cleaners, the motor to draw the dirty air through the vacuum cleaner is positioned in the ground engaging head and the upward extending portion is pivotally mounted to the upper portion of the ground engaging member at a position adjacent the motor.
The advantages of cyclonic separation have been combined with an upright vacuum cleaner to provide a household cyclonic vacuum cleaner, as shown in U.S. Pat. No. 4,593,429 to Dyson. As shown in FIG. 1, this vacuum cleaner 10 essentially comprises a large, outer cylindrical cyclone 12, with an inner cyclone 14 nested therein, which is mounted on a floor-cleaning head and provided with a push handle for convenient movement of the unit. A motor, located in the floor cleaning head, draws air through the cleaning head and into an intake conduit 16, which delivers air to the dirty air inlet 18 of the outer cyclone container 12. From the outer cyclone the air flows into inner, nested dust separating cyclone 14, and from there, continues on through the vacuum motor, which is positioned in the ground engaging member, to a clean air exhaust port.
The air intake conduit 16 connects the floor cleaning head and the dirty air inlet in air flow communication. Air intake conduit 16 extends upwardly along the outside of outer cyclone container 12 generally parallel to the longitudinal axis of the cyclones 12, 14. At a position adjacent air inlet 18 to outer cyclone 12, air intake conduit 16 bends 90° twice to travel inwardly and to provide a tangential air flow to air inlet 18 of outer cyclone container 12.
In use, air intake conduit 16 may become blocked. If the blockage occurs at a midpoint of the conduit, it may be difficult to clear the blockage. While a clean out port may be provided, the port may not be located near where the blockage occurs. Further, the addition of a port increases the cost and complexity of the manufacture of the product.
A bend in a conduit for a fluid causes a turbulent pressure loss in the conduit as the fluid travels through the bend in the conduit and the greater the sharpness of the bend, the greater the pressure loss. The pressure loss in the air flow decreases the amount of suction which can be generated at the cleaning head of the vacuum cleaner for any given motor in the vacuum cleaner and therefore the efficiency of the vacuum cleaner.